/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_lattice_f32.c
*
* Description:	Processing function for the floating-point FIR Lattice filter.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @defgroup FIR_Lattice Finite Impulse Response (FIR) Lattice Filters
 *
 * This set of functions implements Finite Impulse Response (FIR) lattice filters
 * for Q15, Q31 and floating-point data types.  Lattice filters are used in a
 * variety of adaptive filter applications.  The filter structure is feedforward and
 * the net impulse response is finite length.
 * The functions operate on blocks
 * of input and output data and each call to the function processes
 * <code>blockSize</code> samples through the filter.  <code>pSrc</code> and
 * <code>pDst</code> point to input and output arrays containing <code>blockSize</code> values.
 *
 * \par Algorithm:
 * \image html FIRLattice.gif "Finite Impulse Response Lattice filter"
 * The following difference equation is implemented:
 * <pre>
 *    f0[n] = g0[n] = x[n]
 *    fm[n] = fm-1[n] + km * gm-1[n-1] for m = 1, 2, ...M
 *    gm[n] = km * fm-1[n] + gm-1[n-1] for m = 1, 2, ...M
 *    y[n] = fM[n]
 * </pre>
 * \par
 * <code>pCoeffs</code> points to tha array of reflection coefficients of size <code>numStages</code>.
 * Reflection Coefficients are stored in the following order.
 * \par
 * <pre>
 *    {k1, k2, ..., kM}
 * </pre>
 * where M is number of stages
 * \par
 * <code>pState</code> points to a state array of size <code>numStages</code>.
 * The state variables (g values) hold previous inputs and are stored in the following order.
 * <pre>
 *    {g0[n], g1[n], g2[n] ...gM-1[n]}
 * </pre>
 * The state variables are updated after each block of data is processed; the coefficients are untouched.
 * \par Instance Structure
 * The coefficients and state variables for a filter are stored together in an instance data structure.
 * A separate instance structure must be defined for each filter.
 * Coefficient arrays may be shared among several instances while state variable arrays cannot be shared.
 * There are separate instance structure declarations for each of the 3 supported data types.
 *
 * \par Initialization Functions
 * There is also an associated initialization function for each data type.
 * The initialization function performs the following operations:
 * - Sets the values of the internal structure fields.
 * - Zeros out the values in the state buffer.
 * To do this manually without calling the init function, assign the follow subfields of the instance structure:
 * numStages, pCoeffs, pState. Also set all of the values in pState to zero.
 *
 * \par
 * Use of the initialization function is optional.
 * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
 * To place an instance structure into a const data section, the instance structure must be manually initialized.
 * Set the values in the state buffer to zeros and then manually initialize the instance structure as follows:
 * <pre>
 *arm_fir_lattice_instance_f32 S = {numStages, pState, pCoeffs};
 *arm_fir_lattice_instance_q31 S = {numStages, pState, pCoeffs};
 *arm_fir_lattice_instance_q15 S = {numStages, pState, pCoeffs};
 * </pre>
 * \par
 * where <code>numStages</code> is the number of stages in the filter; <code>pState</code> is the address of the state buffer;
 * <code>pCoeffs</code> is the address of the coefficient buffer.
 * \par Fixed-Point Behavior
 * Care must be taken when using the fixed-point versions of the FIR Lattice filter functions.
 * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
 * Refer to the function specific documentation below for usage guidelines.
 */

/**
 * @addtogroup FIR_Lattice
 * @{
 */


/**
 * @brief Processing function for the floating-point FIR lattice filter.
 * @param[in]  *S        points to an instance of the floating-point FIR lattice structure.
 * @param[in]  *pSrc     points to the block of input data.
 * @param[out] *pDst     points to the block of output data
 * @param[in]  blockSize number of samples to process.
 * @return none.
 */

void arm_fir_lattice_f32(
    const arm_fir_lattice_instance_f32 *S,
    float32_t *pSrc,
    float32_t *pDst,
    uint32_t blockSize)
{
    float32_t *pState;                             /* State pointer */
    float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */
    float32_t *px;                                 /* temporary state pointer */
    float32_t *pk;                                 /* temporary coefficient pointer */


#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */

    float32_t fcurr1, fnext1, gcurr1, gnext1;      /* temporary variables for first sample in loop unrolling */
    float32_t fcurr2, fnext2, gnext2;              /* temporary variables for second sample in loop unrolling */
    float32_t fcurr3, fnext3, gnext3;              /* temporary variables for third sample in loop unrolling */
    float32_t fcurr4, fnext4, gnext4;              /* temporary variables for fourth sample in loop unrolling */
    uint32_t numStages = S->numStages;             /* Number of stages in the filter */
    uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

    gcurr1 = 0.0f;
    pState = &S->pState[0];

    blkCnt = blockSize >> 2;

    /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
       a second loop below computes the remaining 1 to 3 samples. */
    while(blkCnt > 0u)
    {

        /* Read two samples from input buffer */
        /* f0(n) = x(n) */
        fcurr1 = *pSrc++;
        fcurr2 = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* Read g0(n-1) from state */
        gcurr1 = *px;

        /* Process first sample for first tap */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext1 = fcurr1 + ((*pk) * gcurr1);
        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext1 = (fcurr1 * (*pk)) + gcurr1;

        /* Process second sample for first tap */
        /* for sample 2 processing */
        fnext2 = fcurr2 + ((*pk) * fcurr1);
        gnext2 = (fcurr2 * (*pk)) + fcurr1;

        /* Read next two samples from input buffer */
        /* f0(n+2) = x(n+2) */
        fcurr3 = *pSrc++;
        fcurr4 = *pSrc++;

        /* Copy only last input samples into the state buffer
           which will be used for next four samples processing */
        *px++ = fcurr4;

        /* Process third sample for first tap */
        fnext3 = fcurr3 + ((*pk) * fcurr2);
        gnext3 = (fcurr3 * (*pk)) + fcurr2;

        /* Process fourth sample for first tap */
        fnext4 = fcurr4 + ((*pk) * fcurr3);
        gnext4 = (fcurr4 * (*pk++)) + fcurr3;

        /* Update of f values for next coefficient set processing */
        fcurr1 = fnext1;
        fcurr2 = fnext2;
        fcurr3 = fnext3;
        fcurr4 = fnext4;

        /* Loop unrolling.  Process 4 taps at a time . */
        stageCnt = (numStages - 1u) >> 2u;

        /* Loop over the number of taps.  Unroll by a factor of 4.
         ** Repeat until we've computed numStages-3 coefficients. */

        /* Process 2nd, 3rd, 4th and 5th taps ... here */
        while(stageCnt > 0u)
        {
            /* Read g1(n-1), g3(n-1) .... from state */
            gcurr1 = *px;

            /* save g1(n) in state buffer */
            *px++ = gnext4;

            /* Process first sample for 2nd, 6th .. tap */
            /* Sample processing for K2, K6.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext1 = fcurr1 + ((*pk) * gcurr1);
            /* Process second sample for 2nd, 6th .. tap */
            /* for sample 2 processing */
            fnext2 = fcurr2 + ((*pk) * gnext1);
            /* Process third sample for 2nd, 6th .. tap */
            fnext3 = fcurr3 + ((*pk) * gnext2);
            /* Process fourth sample for 2nd, 6th .. tap */
            fnext4 = fcurr4 + ((*pk) * gnext3);

            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            /* Calculation of state values for next stage */
            gnext4 = (fcurr4 * (*pk)) + gnext3;
            gnext3 = (fcurr3 * (*pk)) + gnext2;
            gnext2 = (fcurr2 * (*pk)) + gnext1;
            gnext1 = (fcurr1 * (*pk++)) + gcurr1;


            /* Read g2(n-1), g4(n-1) .... from state */
            gcurr1 = *px;

            /* save g2(n) in state buffer */
            *px++ = gnext4;

            /* Sample processing for K3, K7.... */
            /* Process first sample for 3rd, 7th .. tap */
            /* f3(n) = f2(n) +  K3 * g2(n-1) */
            fcurr1 = fnext1 + ((*pk) * gcurr1);
            /* Process second sample for 3rd, 7th .. tap */
            fcurr2 = fnext2 + ((*pk) * gnext1);
            /* Process third sample for 3rd, 7th .. tap */
            fcurr3 = fnext3 + ((*pk) * gnext2);
            /* Process fourth sample for 3rd, 7th .. tap */
            fcurr4 = fnext4 + ((*pk) * gnext3);

            /* Calculation of state values for next stage */
            /* g3(n) = f2(n) * K3  +  g2(n-1) */
            gnext4 = (fnext4 * (*pk)) + gnext3;
            gnext3 = (fnext3 * (*pk)) + gnext2;
            gnext2 = (fnext2 * (*pk)) + gnext1;
            gnext1 = (fnext1 * (*pk++)) + gcurr1;


            /* Read g1(n-1), g3(n-1) .... from state */
            gcurr1 = *px;

            /* save g3(n) in state buffer */
            *px++ = gnext4;

            /* Sample processing for K4, K8.... */
            /* Process first sample for 4th, 8th .. tap */
            /* f4(n) = f3(n) +  K4 * g3(n-1) */
            fnext1 = fcurr1 + ((*pk) * gcurr1);
            /* Process second sample for 4th, 8th .. tap */
            /* for sample 2 processing */
            fnext2 = fcurr2 + ((*pk) * gnext1);
            /* Process third sample for 4th, 8th .. tap */
            fnext3 = fcurr3 + ((*pk) * gnext2);
            /* Process fourth sample for 4th, 8th .. tap */
            fnext4 = fcurr4 + ((*pk) * gnext3);

            /* g4(n) = f3(n) * K4  +  g3(n-1) */
            /* Calculation of state values for next stage */
            gnext4 = (fcurr4 * (*pk)) + gnext3;
            gnext3 = (fcurr3 * (*pk)) + gnext2;
            gnext2 = (fcurr2 * (*pk)) + gnext1;
            gnext1 = (fcurr1 * (*pk++)) + gcurr1;

            /* Read g2(n-1), g4(n-1) .... from state */
            gcurr1 = *px;

            /* save g4(n) in state buffer */
            *px++ = gnext4;

            /* Sample processing for K5, K9.... */
            /* Process first sample for 5th, 9th .. tap */
            /* f5(n) = f4(n) +  K5 * g4(n-1) */
            fcurr1 = fnext1 + ((*pk) * gcurr1);
            /* Process second sample for 5th, 9th .. tap */
            fcurr2 = fnext2 + ((*pk) * gnext1);
            /* Process third sample for 5th, 9th .. tap */
            fcurr3 = fnext3 + ((*pk) * gnext2);
            /* Process fourth sample for 5th, 9th .. tap */
            fcurr4 = fnext4 + ((*pk) * gnext3);

            /* Calculation of state values for next stage */
            /* g5(n) = f4(n) * K5  +  g4(n-1) */
            gnext4 = (fnext4 * (*pk)) + gnext3;
            gnext3 = (fnext3 * (*pk)) + gnext2;
            gnext2 = (fnext2 * (*pk)) + gnext1;
            gnext1 = (fnext1 * (*pk++)) + gcurr1;

            stageCnt--;
        }

        /* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
        stageCnt = (numStages - 1u) % 0x4u;

        while(stageCnt > 0u)
        {
            gcurr1 = *px;

            /* save g value in state buffer */
            *px++ = gnext4;

            /* Process four samples for last three taps here */
            fnext1 = fcurr1 + ((*pk) * gcurr1);
            fnext2 = fcurr2 + ((*pk) * gnext1);
            fnext3 = fcurr3 + ((*pk) * gnext2);
            fnext4 = fcurr4 + ((*pk) * gnext3);

            /* g1(n) = f0(n) * K1  +  g0(n-1) */
            gnext4 = (fcurr4 * (*pk)) + gnext3;
            gnext3 = (fcurr3 * (*pk)) + gnext2;
            gnext2 = (fcurr2 * (*pk)) + gnext1;
            gnext1 = (fcurr1 * (*pk++)) + gcurr1;

            /* Update of f values for next coefficient set processing */
            fcurr1 = fnext1;
            fcurr2 = fnext2;
            fcurr3 = fnext3;
            fcurr4 = fnext4;

            stageCnt--;

        }

        /* The results in the 4 accumulators, store in the destination buffer. */
        /* y(n) = fN(n) */
        *pDst++ = fcurr1;
        *pDst++ = fcurr2;
        *pDst++ = fcurr3;
        *pDst++ = fcurr4;

        blkCnt--;
    }

    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
     ** No loop unrolling is used. */
    blkCnt = blockSize % 0x4u;

    while(blkCnt > 0u)
    {
        /* f0(n) = x(n) */
        fcurr1 = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* read g2(n) from state buffer */
        gcurr1 = *px;

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext1 = fcurr1 + ((*pk) * gcurr1);
        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext1 = (fcurr1 * (*pk++)) + gcurr1;

        /* save g1(n) in state buffer */
        *px++ = fcurr1;

        /* f1(n) is saved in fcurr1
           for next stage processing */
        fcurr1 = fnext1;

        stageCnt = (numStages - 1u);

        /* stage loop */
        while(stageCnt > 0u)
        {
            /* read g2(n) from state buffer */
            gcurr1 = *px;

            /* save g1(n) in state buffer */
            *px++ = gnext1;

            /* Sample processing for K2, K3.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext1 = fcurr1 + ((*pk) * gcurr1);
            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext1 = (fcurr1 * (*pk++)) + gcurr1;

            /* f1(n) is saved in fcurr1
               for next stage processing */
            fcurr1 = fnext1;

            stageCnt--;

        }

        /* y(n) = fN(n) */
        *pDst++ = fcurr1;

        blkCnt--;

    }

#else

    /* Run the below code for Cortex-M0 */

    float32_t fcurr, fnext, gcurr, gnext;          /* temporary variables */
    uint32_t numStages = S->numStages;             /* Length of the filter */
    uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

    pState = &S->pState[0];

    blkCnt = blockSize;

    while(blkCnt > 0u)
    {
        /* f0(n) = x(n) */
        fcurr = *pSrc++;

        /* Initialize coeff pointer */
        pk = pCoeffs;

        /* Initialize state pointer */
        px = pState;

        /* read g0(n-1) from state buffer */
        gcurr = *px;

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext = fcurr + ((*pk) * gcurr);
        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext = (fcurr * (*pk++)) + gcurr;

        /* save f0(n) in state buffer */
        *px++ = fcurr;

        /* f1(n) is saved in fcurr
           for next stage processing */
        fcurr = fnext;

        stageCnt = (numStages - 1u);

        /* stage loop */
        while(stageCnt > 0u)
        {
            /* read g2(n) from state buffer */
            gcurr = *px;

            /* save g1(n) in state buffer */
            *px++ = gnext;

            /* Sample processing for K2, K3.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext = fcurr + ((*pk) * gcurr);
            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext = (fcurr * (*pk++)) + gcurr;

            /* f1(n) is saved in fcurr1
               for next stage processing */
            fcurr = fnext;

            stageCnt--;

        }

        /* y(n) = fN(n) */
        *pDst++ = fcurr;

        blkCnt--;

    }

#endif /*   #ifndef ARM_MATH_CM0_FAMILY */

}

/**
 * @} end of FIR_Lattice group
 */
